The present invention is directed generally to automatic control over an advancing direction of a vehicle which travels on a road surface, and more particularly, to an advancing direction automatic control system for parallel traveling while automatically keeping constant distances to guide means provided on the road surface of a traveling lane or aside of the lane or set in the air along the traveling lane.
With the intention of attaining high-density traveling in which vehicle intervals are shortened on a highway, there have hitherto been proposed automatic parallel traveling control and automatic acceleration/deceleration control, the arrangement being such that: a guide board is disposed along a traveling lane; distances between a vehicle and the guide board and a distance to a preceding vehicle are measured from on the vehicle; a steering shaft is automatically rotationally driven so that the distances between the guide board and the vehicle come to set values; if the distance to the preceding vehicle is large, the vehicle is accelerated by opening a throttle valve; whereas if small, the vehicle is made to travel in parallel with the guide board by automatically effecting wheel braking; and at the same time the inter-vehicle distance is shortened to the greatest possible degree so as to be more than the set value. There have also been proposed automatic parallel traveling control and automatic acceleration/deceleration control wherein a white line on the road surface is picked up on a video picture while photographing the front road surface by means of a TV camera, the steering shaft is automatically rotationally driven so that a distance between the white line and the vehicle of user's own becomes a set value, and opening/closing of the throttle valve and wheel braking are controlled by detecting a front vehicle and obstacles.
In these proposals of the automatic parallel traveling control, if the distance between the vehicle and guide means such as the guide board and the white line deviates from the set value, the steering shaft is automatically rotationally driven to move forward in such a direction as to obviate this deviation. As a result, the driver feels it strange that a steering wheel rotates, though not intended to make revolutions. For instance, in the case of a curved traveling lane, the driver visually recognizes the curvedness and therefore turns the steering wheel to adjust the vehicle to the curvature of the traveling lane. A driver accustomed to power assist steering is not so amazed at the auto-rotation of the steering wheel with no feeling of strangeness. If the vehicle starts deviating from a straight traveling lane due to, e.g., a heavy sideway wind, and thus the steering wheel is automatically rotationally driven to compensate the deviation, it follows that the driver will be alarmed about the abrupt auto-rotation of the steering wheel unless the driver himself or herself recognizes the possible of disturbance in the advancing direction which is caused by the sideway wind at that time. As is broadly known, mental disturbances induced during highspeed traveling are unfavorable in terms of safe driving.
When the driver changes the traveling lane, the steering wheel is automatically rotationally driven in such a direction that the automatic parallel traveling control functions to hinder a change in course that deviates from the lane along which the vehicle is now traveling, as a consequence of which the driver is not allowed to smoothly change the traveling lane. Hence, there are required release operations of returning a parallel traveling indication switch for indicating the auto parallel traveling control to an open state where releasing is designated or putting a separately provided release indication switch into a closed state where the drivers gives an instruction of releasing.
On the occasion of a change in course or exiting from the highway, the necessity for the above-mentioned releasing operations probably adds a danger to driving of the vehicle, and it is therefore desirable that the parallel traveling control be automatically released without requiring special operations.